Toner release oil transfer pad

ABSTRACT

An improved oil applicating pad for use in applying oil to the fuser roll surface of a heated pressure fusing system for fusing toner images. The pad has a working surface made of silicone rubber material which resists visual and non-visual toner offset on the surface thereof. The pad construction includes different embodiments which comprise sponge, reinforced fabric, and multiple layers of different material.

United States Patent [191 Thettu 1 Oct. 15, 1974 1 TONER RELEASE OIL TRANSFER PAD [75] Inventor: Taghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

221 Filed: Junel1,1973

[2]] Appl. No.: 369,024

[52] US. Cl 432/60, 118/266, 118/260,

l01/132.5, 101/422 [51] Int. Cl. B05c 11/00 [58]- Field of Search 432/5962,

[56] References Cited UNITED STATES PATENTS 2,241,554 5/1941 Lang et a1 118/260 2,313,127 3/1943 Denison 118/260 2,533,574 12/1950 Gerlach 118/260 2,534,765 12/1950 Genz 2,704,029 3/1955 George 15/256.5l 3,081,206 3/1963 Remer 29/132 3,449,548 6/1969 Adamek.... 3,573,964 4/1971 Jones 3,637,976 l/1972 Ohta et al.....

3,718,116 2/1973 Thettu 3,731,358 5/1973 Artl .L 101/422 Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen [57] ABSTRACT An improved oil applicating pad for use in applying oil to the fuser roll surface of a heated pressure fusing system for fusing toner images. The pad has a working surface made of silicone rubber material which resists visual and non-visual toner offset on the surface thereof. The pad construction includes different embodiments which comprise sponge, reinforced fabric, and multiple layers of different material.

4 Claims, 5 Drawing Figures TONER RELEASE OIL TRANSFER PAD This application relates to heated pressure fusing systems and in particular to an improved toner release oil transfer pad which resists visual and non-visual toner offset.

In the practice of xerography as described in US. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic surface is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where the light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image can then be developed by contacting it with a finely divided electrostatically attractable material such as a powder. The powder is held in image areas by the electrostatic charges on the layer. Where the charge field is greatest, the greatest amount of powder is deposited. Thus, a powder image is produced in conformity with the light image of the document or object being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably affixed thereto to form a permanent print.

One typical device for fixing the toner particles to the backing sheet is by a heated pressure fuser roll system in which the copy sheet is passed through the nip of a Teflon coated heated fuser roll and a backup roll as described in US. Pat. Nos. 3,256,002 and 3,268,35l. In such fusing systems, care must be taken to remove unwanted toner particles from the heated fuser roll prior to its contact with the copy being fused. If care is not taken to keep the fuser roll free of toner particles, these toner particles can build up on the face of the fuser roll and degrade the quality of the fix by removing the fusing properties on the surface of the roll contacting the copy sheet and toner images. Furthermore, such unwanted toner particles can be release from the fusing roll upon its subsequent contact with the toner image to fuse toner particles to the copy sheet in non-imaged areas which results in copy defects. A wick is generally used to dispense silicone oil on the external surface of the heated fuser roll by a pad overlying the heated fuser roll.

In the past the oil applicating pad surface has become contaminated with toner offset which is both visual where sufficiently high in density and non-visual where sufficiently low in density. The non-visual offset is the primary cause ofthe contamination on the oil applicating pad surface because the visual toner offset will normally remain on the fuser roll surface rather than on the Teflon oil pad. As a result the situation can be corrected only by lowering the temperature range during the fusing operation when the visible offset is sighted on the copy sheets. It will be appreciated that the nonvisual toner offset cannot be easily sighted by the naked eye and that continued accumulation of this non-visual toner offset onto the pad surface alternatively leads to a visual film that prevents oil application to the fuser roll surface. As a result a failure of the oil applicating pad is not noticed until the pad is no longer effective and requires replacement.

It is therefore an object of the present invention to improve heated pressure fusing systems.

It is another object of the present invention to improve oil applicating characteristics of wicking assemblies for use with heated pressure fusing systems.

It is another object of the invention to extend the life of oil applicating wicking assemblies used in heated pressure fusing systems.

It is still another object of the present invention to retain the oil applicating properties of a wicking pad in a heated pressure fusing system over long periods of 4 time.

It is still another object of the present invention to prevent non-visual and visual toner offset onto the oil applicating pad of heated pressure fusing systems.

It is still another object of the invention to eliminate premature replacement oil applicating pads for heated pressure fusing systems.

It is still another object of the present invention to minimize costs and unnecessary maintenance of copier/duplicator systems.

These and other objects of the instant invention are obtained by a new and improved wicking assembly which comprises a layer of silicone rubber which contacts the heated fuser roll on one side and is in contact with silicone oil on the other side.

Further objects of this invention together with additional features and advantages thereof will become apparent from the following detailed description of the embodiment of the inventionwhen read in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic representation of an automatic xerographic reproducing machine incorporating a heated pressure fusing system utilizing the improved wicking assembly of the present invention;

FIG. 2 is a side elevational view of the heated pressure fusing system;

FIG. 3 (a) is an exploded view of the silicone rubber pad of the present invention;

FIG. 3 (b) is an exploded view similar to FIG. 3 (a) illustrating an alternative embodiment of the pad; and

FIG. 4 is an isometric view of an alternative embodiment of the oil applicating pad assembly illustrating a plurality of applicating layers.

Referring now to FIG. 1 of the drawings there is shown an embodiment of the invention in a suitable environment such as an automatic xerographic reproducing machine. The automatic reproducing machine includes a xerographic plate or surface 10 formed in'the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing journaled in a frame to rotate in a direction indicated by the arrow. The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations. For purposes of the present disclosure the several xerographic processing stations in the path of movement of the plate surface may be described functionally as follows:

A charging station A which the uniform electrostatic charge is deposited onto the photoconductive plate;

An exposure station B at which light or radiation pattern of copies to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copies to be reproduced;

A developing station C at which xerographic developing material including toner particles having an electrostatic charge opposite to that of the latent electrostatic image is cascaded over thelatent electrostatic image to form a powdered image in configuration of the copy being reproduced;

A transfer station D which the powdered image is electrostatically transferred from the plate surface to a transfer material such as paper which is then passed through a heated pressure fusing system having an improved oil applicating pad according to the present invention as will be described hereinafter; and

A drum cleaning and discharge station E at which the plate surface is brushed to remove residual toner parti- -cles remaining thereon after image transfer and at which the plate is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

For further details of the xerographic processing station above reference is made to U.S. Pat. No. 3,645,615 filed July 3, l969 and commonly assigned herewith.

Referring now in particular to FIG. 2 there is shown the heated pressure fusing system of the present invention which includes a heated fuser roll 16 and a backup pressure roll 18. Fuser roll 16 is a hollow circular cylinder with a metallic core 20 and a Teflon layer 22. A quartz lamp 24 serves as a source of thermal energy and is located at the center of the fuser roll. Power to the lamp is controlled by a thermal sensor generally called a thermister contacting the periphery of the fuser roll as described, for example, in U.S. Pat. No. 3,357,249. The backup roll 18 is also a circular cylinder and is made up of a metal core surrounded by a thick rubber layer 32 and also a Teflon layer 34 to prevent soaking silicone oil into rubber layer 32 and subsequent swelling.

When the two rollers 16 and 18 are engaged as shown in FIG. 2 the applied load deforms the rubber in the pressure mil to provide the nip with a finite width. The copy sheet 40 electrostatically bearing the toner images 42 on the underside is brought into contact with the nip of the rolls with the toner image contacting the fuser roll 16. For a given temperature of the fuser roll, the fusing rate will depend upon the contact arc length of the support material against the dwell time, i.e. the time the toner images remain between the fuser roll 16 and the backup roll 18. Dwell time can be varied either by changing the surface velocity of the rolls or by varying the contact arc length and holding the speed of the roll the same. Contact arc length depends on the softness of the rubber on backup roll 18 and on the amount of pressure between the rolls 16 and 18. The mechanism for driving the rolls and for lowering and raising the rolls into contact can be accomplished by any suitable means as that described, for example, in U.S. Pat. No. 3,291,466 or by a suitable mechanical cumming device.

As a sheet of material is advanced between the rolls l6 and 17 the toner images on the support material will contact the peripheral heated surface of the roll 16 whereby the toner images become tackified and in this 65 tackified condition the toner will tend to offset on this roll except that it is partially prevented from doing so by the Teflon coating on the roll.

In the past both toner visual and non-visual offset has collected onto the oil pad applicating surface obstructing the flow of oil onto the fuser roll. By the oil pad apparatus of the present invention a thin film of offset preventing silicone oil is applied to the surface 22 of the fuser roll 16 while preventing both visual and nonvisual offset onto the pad surface as will be described hereinafter.

An oil dispensing apparatus 45 includes wicking assembly 48, an oil pan for maintaining a supply of silicone oil 51 and an applicator roll 52. The oil pan is loaded against the heated fuser roll 16 by a spring action mounting (not shown) as details of the mounting form no part of the present invention. Applicator roll 52 is used to convey a thin film of oil to the bottom face 55 of the wicking assembly as the applicator roll is rotated in the direction shown by the arrow. Desirably, the applicator roll 52 is driven by an oil dispensing motor 58 which is energized during the fusing operation for a period depending upon the number of copies being produced.

In accordance with the present invention, the wicking assembly 48 includes an oil applicating layer 62 made of silicone rubber with an embossed or rippled pattern 63 which contacts the surface of the heated fuser roll 16. The oil applicating layer 62 prevents both visual and non-visual toner collection on its surface so that no restriction is placed on its ability to continually apply a thin film of silicone oil as a release agent on the fuser roll surface. While the phenomena of nonadhesion of toner to silicone rubber material is not completely understood, it has been observed that toner when tackified adheres to the fuser roll surface rather than to the silicone material surface.

Desirably the silicone rubber layer 62 can take the form of aunitary pad construction as shown in H0. 3(b). The reinforced construction includes a iayer of silicone rubber 81 having a reinforced fiber 82 arranged in a crossed, woven or knitted pattern andwhich is molded in the silicone rubber layer. Fiber members 82 may be made of any suitable heat stable material. Suitable material are ceramic, metallic, plastic or combinations thereof.

A further embodiment of the invention is shown in FIG. 4 which incorporates a plurality of oil applicating layers 92 and 94. Layer 94 is made of a suitable heat stable material with high oil transfer properties. Layer 94 has its underside 55 in contact with the applicator roll 52 and its upperside in contact with silicone rubber layer 92. Layers 92 and 94 are assembled in overlapping relationship and their ends are clamped between plates 66 and 68 which are secured by any suitable means such as screws 70.

While the instant invention as to its objects and advantages has been described as being carried in a speciiic embodiment thereof it is not intended to be limited thereby but it is intended to be covered broadly within the scope of the appended claims.

What is claimed is:

1. In a heated pressure roll fusing system for fusing toner images to copy sheets of an eiectrostatic copying machine in which a heated fuser roll is coated with an oil to prevent toner offset, an improved oil application pad comprising.

an oil transfer pad member positioned in contact with a heated fuser roll to apply oil received by said pad member eontinuouslyto the surface of said heated 3. A pad device according .to claim 2 wherein said fibers are made of a material selected from a group comprising, ceramic, metallic, plastic or combinations thereof.

4. A pad device according to claim 1 wherein said pad member includes a plurality of layers, at least one of said layers being made of a heat stable material other than silicone rubber.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,841,827

DATED October 15, 1974 INVENTO R(S) Raghulinga R. Thettu i It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Heading after "Inventor:" change "Tahulinga R. Thettu" to -Raghulinga R. Thettu-.

EI'gncd and Scaled this [SEAL] Seventh D y Of 0cmber1975 Attest:

RUTH C. MASON ommissioner oj'Patents and Trademarks 

1. In a heated pressure roll fusing system for fusing toner images to copy sheets of an electrostatic copying machine in which a heated fuser roll is coated with an oil to prevent toner offset, an improved oil application pad comprising an oil transfer pad member positioned in contact with a heated fuser roll to apply oil received by said pad member continuously to the surface of said heated fuser roll during fusing of toner images to copy sheets, said pad member having a working surface contacting said heated fuser roll made of silicone rubber sponge material which has an embossed pattern to resist visual and non-visual offset accumulation on the surface thereof.
 2. A pad device according to claim 1 wherein said pad member comprises a silicone rubber sponge layer reinforced by fibers.
 3. A pad device according to claim 2 wherein said fibers are made of a material selected from a group comprising, ceramic, metallic, plastic or combinations thereof.
 4. A pad device according to claim 1 wherein said pad member includes a plurality of layers, at least one of said layers being made of a heat stable material other than silicone rubber. 